Oil-shale, one of the leading sources under investigation for the production of synthetic fuels, may play a leading role in the energy future of the United States. The primary reason for the growing importance of oil-shale, as well as coal, is the rapid depletion of known petroleum and natural gas reserves. These known reserves are being depleted at a faster rate than the rate of discovering new reserves. As the era of petroleum growth draws to a close, the world's energy mix will have to change. Transition energy sources will be needed as a bridge between petroleum and the potentially unlimited energy sources of the future; such sources being, for example, solar power and nuclear fusion. Owing to their great abundance, coal and oil-shale are perceived as the keystones of such a bridge. Consequently, a great deal of research and development is presently in progress to provide economical ways of converting these solid resources to valuable liquids and gases.
Generally, oil is produced from oil-shale by heating the oil-shale in either a fixed or moving bed reactor at a temperature from about 450.degree. C. to 550.degree. C. for a long enough time to convert the organic matter to gas, oil, and residual carbon on spent shale.
Although myriad other process exist for obtaining oil from oil-shale, all of these processes result in: (i) a shale-oil which faces severe problems in up-grading because of a relatively high concentration of nitrogen, and (ii) a spent shale having an unacceptable level of nitrogen, sulfur, or both. This nitrogen and sulfur could generate undesirable levels of nitrogen and sulfur oxide pollutants if the spent shale is combusted for its fuel value.